Plastic shot shell and base wad

ABSTRACT

A shot shell having a tubular casing made of hard polycarbonate plastic and terminating at its lower end at an integral base wall formed to provide an inwardly and axially projecting primer pocket is provided with a soft, yieldable polyethylene base wad having an axially extending central passage within which said primer pocket is received. The concave top surface of the base wad has a central aperture of smaller diameter than said axially extending passage, thereby defining an annular shoulder which abuts against the top of said primer pocket in sealing contact therewith. The aforesaid central aperture in the top of the base wad has a diameter at least equal to that of the inside of the primer pocket to thereby provide an unrestricted flash passage above a primer cap inserted into the primer pocket. An annular clearance space between the axial passage in the base wad and the tubular primer pocket in combination with a plurality of longitudinally spaced peripheral teeth on the base wad provide expansion room into which the resilient base wad may be compressed downwardly to provide a cushioning and shock absorbing effect that protects the lower end and base wall of the hard plastic casing from the pressures generated by the exploding propellant charge within the casing.

United States Patent I [111 3,590,740

[72] Inventor George L. llerter OTHER REFERENCES wlsecav The All PlaticWanda Shotshells by Wallace Labisky; 11 391 2 968 reprint from SHQQTINGTIMES, Nov. 1967; copy in 102/42 e 0 r ublications 4s Patented July 6,1971 p [73 1 A i gnu-5 1 Primary Examiner-Robert F. Stahl w MiArI0rneyWrlliamson, Palmatier and Bains ABSTRACT: A shot shell having atubular casing made of hard polycarbonate plastic and terminating at itslower end at an integral base wall formed to provide an inwardly andaxially projecting primer pocket is provided with a soft, yieldabie [54]PLASTIC SHOT SHELL AND A W D polyethylene base wad having an axiallyextending central 2 Claims, 4 Drawing Figs. passage within which saidprimer pocket is received. The con- 52 115.0 102/44, cave toP Surfacethe base wad has a central aperture of 02/42 C1 102195 02/43 P smallerdiameter than said axially extending passage, thereby 5| Int. Cl F42b7/08, defining annular Shoulder which abuts against the F42) 9/30 saidprimer pocket in sealing contact therewith. The aforesaid 50 Field ofSearch l02/38, 43, central aperture in the top the base Wad has adiamete at 43 p 44 9 5 42 least equal to that of the inside of theprimer pocket to thereby provide an unrestricted flash passage above aprimer cap in- [56] References Cited serted into the primer pocket. Anannular clearance space UNlTED STATES PATENTS between the axial passagein the base wad and the tubular primer pocket in combination with aplurality of longitudinally gsggzgfii' I spaced periplllieral teeth thebase :d provide expansiog 3 359 906 12/1967 Herter 102/95 room w i wamay be compfesse downwardly to provide a cushlomng and shock absorbingef- FOREIGN PATENTS fact that protects the lower end and base wall ofthe hard 1,294,551 7/ 1961 France 102/43 P plastic casing from thepressures generated by the exploding 1,308,189 12/ 196i France 102/42propellant charge within the casing.

PLASTIC SI-IOT SHELL AND BASE WAD BACKGROUND OF THE INVENTION Numerousattempts have been made to manufacture a plastic shot shell casing whichwill not be ruptured or deformed by the pressures generated by theexpanding gases of a propellant charge detonated within the casing. Theproblem becomes particularly acute when the shell casing is manufacturedfrom hard and unyielding polycarbonate plastic. In order to avoid damageto the head or base end of the shell casing, pressure-absorbing basewads of various designs have been installed .within the lower end of thecasing adjacent the base wall. Prior art-base wad designs have beendeficient to the extent that they provide neither an adequate cushioningeffect nor a proper seal around the primer cap. If the base wad does notseal tightly around the primer, expanding gases from the detonatedpowder charge will escape rearwardly with a resultant wastefuldissipation of energy and possible damage to the base of the shellcasing. The problem BRIEF SUMMARY OF THE INVENTION Having in mind theaforesaid problems associated with the manufacture and use of shotshells having hard plastic casings, l have designed a polycarbonateshell casing and plastic base wad which cooperate in such a way as toprevent the transmission of excessive gas pressure to the lower end ofthe casing and to tightly contain the detonated gases within the desiredspace above the primer cap.

These basic objectives are realized by utilizing a soft, yieldablepolyethylene base wad of annular shape which seats snugly around atubular primer pocket which is formed integrally with the casing basewall and projects from the center thereof upwardly into the casing. Thepolyethylene material of the base wad is sufficiently yieldable andresilient that it will compress and deform under the pressures generatedby an exploding charge so as to cushion the hard plastic casing anddis-- tribute the shock waves evenly thereto.

As a particularly beneficial feature of my invention, I enhance thecushioning effect of the polyethylene base wad by providing an annularclearance space between the inside, tubular wall of the base wad and theprimer pocket into which the polyethylene material may flow as it issubjected to detonation pressures. Also, axially spaced, peripheralteeth on the base wad lend it additional compressability and shockabsorbing capacity.

A further beneficial aspect of my invention resides in the provision ofan annular shoulder in the top wall of the base wad which abuts againstthe top of the primer pocket in sealing contact therewith to prevent therearward flow of detonated gases around the primer cap. This sealingshoulder, in combination with the sealing effect obtained from tightengagement of the aforesaid peripheral teeth of the base wad with theinside surface of the plastic casing insures that no 2 BRIEF DESCRIPTIONOF THE DRAWINGS FIG. 1 is an elevation view, partially in section,showing the improved plastic shot shell and base wad of my invention;

FIG. 2 is a bottom perspective view of my improved base wad;

FIG. 3 is a horizontal section view of the lower end of the shot shelltaken along lines 3-3 of FIG. 1; and

FIG. 4 is a fragmentary section view of the lower end of the shot shellshowing on an enlarged scale the form which the yieldable base wad willassume upon detonation of the propellant charge.

In FIG. [of the drawings I have shown a shot shell having an all plasticouter casing 1 with an integral base wall 2. An annular flange 3 on theperiphery of base wall 2 serves as a contact element for an ejectionmechanism in a shotgun. Casing 1 may be rolled over at its upper end 4and provided with a top closure member, not shown. Projecting axiallyinto casing 1 from the center of base wall 2 and formed integrallytherewith is a tubular projection 6 which serves as a primer pocketwithin which primer cap 8 is inserted. Tubular casing l is preferablymolded from hard, impact-resistant polycarbonate, with base wall 2 andprimer pocket 6 being formed integrally therewith.

Disposed within casing 1 is a shot cup 10 which contains a shot charge12 and is shown, for illustrative purpose only, as being part of aunitary overpowder wad, spacer, and shot cup device generally indicatedby reference numeral 14. Device 14 is also preferably formed from amolded plastic such as polyethylene and includes a downwardly dependingoverpowder wad l6. Cooperating with overpowder wad 16 to conline apowder charge 18 therebetween is a base wad 20.

As may be noted with reference to FIGS. 2 and 3 as well as FIG. 1 basewad 20 is of annular shape and has an elongated central passage 22extending axially thereof. As is indicated in FIG. 2, the annular bottom24 of base wad 20 is substantially planar, this shape being given tobottom wall 24 n order to permit it to conform to and seat againstplanar base wall 2 of casing 1 in the manner shown in FIG. 1. With basewad 20 seated in the bottom of tubular casing 1, tubular primer pocketprojection 6 will be received within axial passage 22. As may be notedwith respect to FIG. I, the tubular wall forming axial passage 22 ofbase wad 20 is of slightly greater diameter than the outside of tubularprojection 6, thereby providing an annular clearance space therebetween.This clearance space operates to improve the compressability of base wad20 as will be understood from the description of the operation of basewad 20 hereinafter set forth. Upper wall 26 of base wad 20 has a concaveshape shown most clearly in FIGS. 1 and 3. At the center of concave wall26 is a circular aperture 28 which is of somewhat smaller diameter thanaxial passage 22. By virtue of this construction an annular shoulder 30is formed at the upper end of base wad 20. Shoulder 30, which appearsmost clearly in FIG. 2, abuts against the top of tubular primer pocket 6and assists in sealing gases within propellant chamber 18 in a mannerhereinafter explained. Circular aperture 28 has a diameter at least asgreat as the inside diameter of primer pocket 6 so as to thereby insurean unrestricted flash passage through which flames from detonated primercap 8 may pass upwardly into propellant chamber 18. To further improvethe compressability and scaling function of base wad 20, it is formedwith a plurality of axially spaced sealing rings 32 extending around itsperiphery. Sealing teeth or rings 32 fit snugly against the inside wallof casing l, and being flexible and yieldable may be forced into tightengagement with casing 1 under the influence of the exploding propellantcharge.

The gas pressure generated by the detonation of propellant charge 18will compress and deform polyethylene base wad 20 from the shape shownin FIG. I to that illustrated on an enlarged scale in FIG. 4. Teethlikesealing rings 32 will be forced downwardly and pressed together tothereby provide a cushioning and shock absorbing effect as top, concavewall 26 of base wad 20 is urged downwardly to the position shown in FIG.4. Due to its concave shape, top wall 26 will also receive and transmitforce radially outwardly with the result that sealing rings 32 will beforced into tight contact with the inside surface of casing 1. Aneffective seal will thus be provided along the lower, inside surface ofcasing l to prevent expanding gases from flowing downwardly between basewad and easing 1 towards base wall 2. The downward pressure exerted bythe expanding gases on detonation will also force annular shoulder 30into tight, sealing engagement with the top end of tubular primer pocket6. The tight seal thereby provided between shoulder 30 and primer pocket6 prevents the downward leakage of combustion gases along the outsidewall of primer pocket 6. Because relatively soft and deformablepolyethylene shoulder 30 is seating against plastic primer pocket 6, aparticularly effective and improved seal is obtained at this point ascompared to that which would be achieved if shoulder 30 were abuttingagainst the top of metallic primer cap 8. The cushioning and shockabsorbing capability of polyethylene base wad 20 is further enchanced byproviding the annular clearance space shown in FIG. 1 between tubularwall 22 and the outside surface of primer pocket 6. The downwardpressure acting on base wad 20 at the time of detonation will not onlyforce sealing rings 32 downwardly but will also compress the annularbody of base wad 20 to such an extent that the polyethylene materialthereof will flow into the annular clearance space around primer pocket6. Since bottom wall 24 of base wad 20 is normally seated against theinside surface of casing base wall 2, the compression of annular basewad 20 in a downward direction is limited and it is thus forced todeform radially inwardly, thus filling the annular clearance spacearound primer pocket 6 in the manner shown in FIG. 4. Theplastic-to-plastic contact of base wad inner wall 22 along the wholelength of the outside wall of primer pocket 6 provides a very good sealto further insure against the downward leakage of exploding gases.Polyethylene base wad 20, being resilient as well as yieldable anddeformable, will return to its normal shape after the shot shell inwhich it is used has been fired.

It will thus be seen that yieldable, polyethylene base wad 20 of theparticular configuration shown and described cooperates with the lowerend of polycarbonate casing l and plastic primer pocket 6 in a uniqueway to very effectively shield the lower end of casing l and itsintegral base wall 2 from the potentially damaging effects of theexploding propellant charge. The sealing and shock absorbing functionsof polyethylene base wad 20 in cooperation with plastic primer pocket 6are especially important and critical when using a hard, unyieldingpolycarbonate casing l which is particularly susceptible to deformationand rupture and which is not protected by a tubular metal head over itsbase end.

lclaim:

l. A shot shell comprising:

a tubular casing made entirely of hard, polycarbonate plastic, saidcasing terminating at its lower end at an integral base wall having aperipheral flange of larger diameter than said casing;

a tubular primer pocket extending axially into said casing from thecenter of said base wall, said primer pocket being formed integrallywith said base wall;

an annular base wad having an elongated central passage within whichsaid tubular primer pocket is received and a bottom surface conformingto the inside surface of said base wall and seated there against insurrounding relation to said primer pocket, said base wad being madefrom relatively soft, yieldable and resilient plastic an having anannular shoulder at the center thereof resting upon the top of saidtubular pocket in sealing contact therewith, and the inside diameter ofsaid shoulder being at least as great as the inside diameter of saidtubular pocket;

a powder charge within said casing on top of said base wad;

and

a plurality of continuous resilient teeth closely spaced longitudinallyalong said base wad and extending circumferentially about its periphery,said teeth being arranged in sealin contact with the inside surface ofsaid casing. 2. A shot sfiell as defined in claim 1 wherein:

the inside wall surface of said elongated central passage of said basewad is disposed radially outwardly from the outside surface of saidtubular primer pocket for a substantial portion of the length thereof soas to define an elongated, annular clearance space therebetween intowhich the plastic material of said base wad may flow as it is compressedby the pressure generated by said powder charge exploding within saidcasing.

1. A shot shell comprising: a tubular casing made entirely of hard,polycarbonate plastic, said casing terminating at its lower end at anintegral base wall having a peripheral flange of larger diameter thansaid casing; a tubular primer pocket extending axially into said casingfrom the center of said base wall, said primer pocket being formedintegrally with said base wall; an annular base wad having an elongatedcentral passage within which said tubular primer pocket is received anda bottom surface conforming to the inside surface of said base wall andseated there against in surrounding relation to said primer pocket, saidbase wad being made from relatively soft, yieldable and resilientplastic an having an annular shoulder at the center thereof resting uponthe top of said tubular pocket in sealing contact therewith, and theinside diameter of said shoulder being at least as great as the insidediameter of said tubular pocket; a powder charge within said casing ontop of said base wad; and a plurality of continuous resilient teethclosely spaced longitudinally along said base wad and extendingcircumferentially about its periphery, said teeth being arranged insealing contact with the inside surface of said casing.
 2. A shot shellas defined in claim 1 wherein: the inside wall surface of said elongatedcentral passage of said base wad is disposed radially outwardly from theoutside surface of said tubular primer pocket for a substantial portionof the length thereof so as to define an elongated, annular clearancespace therebetween into which the plastic material of said base wad mayflow as it is compressed by the pressure generated by said powder chargeexploding within said casing.